Particle-based display (PBD) technology has drawn a great deal of attention in display industries in recent years. Due to its wide viewing angles, low power consumptions, light weight, and thin thickness, PBDs have found widespread applications in a variety of fields, for example, in electronic readers, electronic papers, electronic tags, electronic signages, and the like. PBDs are capable of providing visual effects similar to that of paper reading. Different from backlight-type flat panel displays, PBDs utilize reflected ambient light from pigment particles to display content, and thus, there is no glare or other effects resulted from strong external light which affect reading. In addition, PBDs consume power only when the displayed contents are subjected to change.
A PBD includes a plurality of independently addressable display cells spatially arranged in the form of a matrix and disposed between a pair of opposed, spaced-apart substrates, and electrodes disposed on at least one substrate, where each display cell is filled with charged pigment particles in two or more colors. When, by applying voltages onto the electrodes, an electric filed is generated between the pair of substrates, the charged pigment particles in the cells migrate by attraction to the respective electrodes having opposite polarities. Thus, the locations of the pigment particles can be controlled by changing the polarities of the electrodes, thereby displaying images of the reflected light from the pigment particles or fluid.
Based on media that suspend/disperse the pigment particles in the cells, PBDs can be grouped into electrophoretic displays or dry powder type displays.
The electrophoretic displays include microcup electrophoretic displays and microcapsule electrophoretic display. In a microcup electrophoretic display, charged pigment particles (usually in white color) are dispersed in a colored fluid, which in turn, is filled in microcup display cells. The microcup display cells are then sealed between the pair of electrodes. The migrations of the pigment particles in the fluid are controlled by changing the voltage difference between the pair of electrodes, so as to achieve image displaying. For the microcup electrophoretic display, in addition to a slow response time of image displaying due to the slow migration of the pigment particles in the fluid, it is difficult to achieve the uniform dispersion of the pigment particles in the fluid. Even if the amount of the fluid filled in each cell is precisely controlled, there are still differences in the numbers of the pigment particles in each cell, which reduces the uniformity of the particle filling. Therefore, for the microcup electrophoretic display, the particles filling process is complicated and difficult to control, thereby increasing manufacturing costs. Also, the uniformity of the particle dispersion is yet to be further improved.
In a microcapsule electrophoretic display, two types of charged pigment particles of white and black colors with opposed polarities are filled and packaged in microcapsule display cells containing a solvent, which are sandwiched between a pair of electrodes. By changing the voltage difference between the pair of electrodes, the pigment particles can be suspended or fell in the microcapsule cells so as to achieve image displaying. Similarly, the microcapsule electrophoretic display has a slow response time of image displaying due to slow motions of the pigment particles in the solvent. Further, particle aggregation exists, thereby causing the instability of the dispersion of the pigment particles in the solvent, which in turn, affects the yield rate of production.
As for a dry powder type display, each display cell is filled with two colored particles (e.g., black and white) having charges with opposite polarities, respectively. The floating state and the falling state of the different colored particles in the cells are controlled by varying external electric fields imposed on the pigment particles, thereby achieving image displaying. In order to overcome the drawbacks of the slow responses of the electrophoretic displays, the pigment particles in the dry powder type displays are selected to have better flowability and floodability. As such, the pigment particles have the characteristic of fluid, and thus move fast when driven by an electric field. However, during the filling process, the pigment particles may be dispersed or spread all over the cells, i.e., the falling of the pigment particles is not along straight line even under the effect of the gravity. In addition, the black and white colored particles having charges with opposite polarities may easily aggregate together because of the electrostatic attraction, which makes the filling of the pigment particles difficult and affects the yield of production. Lowering the charge density of the pigment particles may reduce the electrostatic attraction generated particle aggregation, however, it will reduce the sensitivity of the pigment particles to a driving electric field, which will result in slow responses. Otherwise, the pigment particles need being driven with high voltages. Indeed, it presents a great challenge in the particle filling process to uniformly fill the black and white colored particles having charges of opposite polarities in each display cell. It would gain a great deal of industrial relevance if simplified processes for filling of the pigment particles uniformly and packaging of the particle-filled cells in the PBDs would be available.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.